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Abstract:

Disclosed are a radiation heat dissipation LED structure and a
manufacturing method thereof. The radiation heat dissipation LED
structure includes a sapphire substrate, an LED epitaxy layer, a base
substrate, a radiation heat dissipation film, and a thermally conductive
binding layer provided between the sapphire substrate and the radiation
heat dissipation film to bind the sapphire substrate and the base
substrate. The radiation heat dissipation film consists of a mixture of
metal and nonmetal. The surface of the film has a microscopic structure
with crystal, which has high efficiency of heat dissipation and can fast
transfer the heat generated by the LED epitaxy layer outwards through the
base substrate by thermal radiation. Therefore, the working temperature
of the LED epitaxy layer is greatly reduced so as to improve the
efficiency of light emitting and the lifetime.

Claims:

1. A radiation heat dissipation LED (light emitting diode) structure,
comprising: a sapphire substrate; an LED epitaxy layer formed on the
sapphire substrate, comprising at least an N type semiconductor layer, a
semiconductor light emitting layer and a P type semiconductor layer,
which are sequentially stacked, wherein the semiconductor light emitting
layer emits light when the LED epitaxy layer is forward biased; a base
substrate; a radiation heat dissipation film formed on the base
substrate; a thermally conductive binding layer provided between the
sapphire substrate and the radiation heat dissipation film to bind the
sapphire substrate and the radiation heat dissipation film; at least one
electrical connection line electrically connecting the N type
semiconductor layer and the P type semiconductor layer to a positive end
and a negative end of an external power source, respectively; and a
package body enclosing the LED epitaxy layer, wherein the radiation heat
dissipation film consists of a mixture of metal and nonmetal, which
consists of at least one of silver, copper, tin, aluminum, titanium, iron
and antimony, and one of oxide, nitride and inorganic acid of at least
one of boron and carbon, and the radiation heat dissipation film has a
microscopic structure with crystal.

2. The radiation heat dissipation LED structure as claimed in claim 1,
wherein the radiation heat dissipation film contains the crystal with a
grain size between one nanometer and tens of micrometers, and a
difference between thermal expansion coefficients of the base substrate
and the radiation heat dissipation film is not greater than 0.1%.

3. The radiation heat dissipation LED structure as claimed in claim 1,
wherein the base substrate is connected to a heat sink.

4. A manufacturing method of a radiation heat dissipation LED structure,
comprising: forming an LED epitaxy layer on a sapphire substrate, wherein
the LED epitaxy layer consists of at least an N type semiconductor layer,
a semiconductor light emitting layer and a P type semiconductor layer,
and the semiconductor light emitting layer emits light when the LED
epitaxy layer is forward biased; forming a radiation heat dissipation
film on a base substrate; and binding the sapphire substrate and the
radiation heat dissipation film by a thermally conductive binding layer
to form the radiation heat dissipation LED structure; wherein the
radiation heat dissipation film consists of a mixture of metal and
nonmetal, which consists of at least one of silver, copper, tin,
aluminum, titanium, iron and antimony, and one of oxide, nitride and
inorganic acid of at least one of boron and carbon, and the radiation
heat dissipation film has a microscopic structure with crystal.

5. The method as claimed in claim 4, wherein the radiation heat
dissipation films contains the crystal with a grain size between one
nanometer and tens of micrometers, and a difference between thermal
expansion coefficients of the radiation heat dissipation film and the
base substrate is not greater than 0.1%.

6. The method as claimed in claim 4, wherein the base substrate is
connected to a heat sink.

7. A radiation heat dissipation LED structure, comprising: a sapphire
substrate having an upper surface and a lower surface; an LED epitaxy
layer formed on the upper surface of the sapphire substrate, consisting
of at least an N type semiconductor layer, a semiconductor light emitting
layer and a P type semiconductor layer, which are sequentially stacked,
wherein the semiconductor light emitting layer emits light when the LED
epitaxy layer is forward biased; a first radiation heat dissipation film
formed on the lower surface of the sapphire substrate; a base substrate;
a second radiation heat dissipation film formed on the base substrate; a
nano-enamel layer formed on the second radiation heat dissipation film; a
thermally conductive binding layer provided between the first radiation
heat dissipation film and the nano-enamel layer to bind the first
radiation heat dissipation film and the nano-enamel layer; at least one
electrical connection line electrically connecting the N type
semiconductor layer and the P type semiconductor layer to a positive end
and a negative end of an external power source, respectively; and a
package body enclosing the LED epitaxy layer, wherein each of the first
and second radiation heat dissipation films consists of a mixture of
metal and nonmetal, which consists of at least one of silver, copper,
tin, aluminum, titanium, iron and antimony, and one of oxide, nitride and
inorganic acid of at least one of boron and carbon, and each of the first
and second radiation heat dissipation films has a microscopic structure
with crystal.

8. The radiation heat dissipation LED structure as claimed in claim 7,
wherein each of the first and second radiation heat dissipation films
contains the crystal with a grain size between one nanometer and tens of
micrometers.

9. The radiation heat dissipation LED structure as claimed in claim 7,
wherein a difference between thermal expansion coefficients of the first
radiation heat dissipation film and the sapphire substrate is not greater
than 0.1%, and another difference between thermal expansion coefficients
of the second radiation heat dissipation film and the base substrate is
not greater than 0.1%.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a radiation heat
dissipation LED (light emitting diode) structure and a manufacturing
method thereof, and more specifically to a radiation heat dissipation LED
structure having a radiation heat dissipation film to enhance the cooling
effect through thermal radiation.

[0003] 2. The Prior Arts

[0004] Recently, LED has been widely applied to various fields due to the
advantage in power saving and carbon reducing, and is also selected as
one of the possible light sources to replace the traditional light bulb.

[0005] As shown in FIG. 1, the LED structure 1 in the prior arts generally
includes an LED chip 10, a sapphire substrate 20, a sliver paste 30, a
leadframe 40, a base substrate 50, connection lines 60, a package body 70
and an aluminum heat sink 80. The LED chip 10 is formed on the sapphire
substrate 20 and is bound with the leadframe 40 by the sliver paste 30.
The base substrate 50 supports the leadframe 40. The connection lines 60
are used to connect the LED chip 10 to the leadframe 40. The leadframe 40
has an extension structure penetrating through the base substrate 50 to
contact the aluminum heat sink 80 under the base substrate 50. The heat
generated by the LED chip 10 is thus transferred to the aluminum heat
sink 80 by thermal conduction, as the heat propagation direction H shown
in FIG. 1.

[0006] However, one of the shortcomings in the prior arts is that the LED
structure 1 may become considerably huge and heavy because the efficiency
of heat dissipation depends on the effective surface area for heat
dissipation if the heat is transferred primarily by thermal conduction.
This may limit the actual application. In addition, the surface area of
the aluminum heat sink 80 usually has a huge geometrical shape and the
total size of the LED structure 1 is thus further increased such that the
LED structure 1 becomes much heavier.

[0007] Therefore, it is strongly desired to provide a new radiation heat
dissipation LED structure and a method of manufacturing the same improve
the efficiency of heat dissipation by thermal radiation without leadframe
or aluminum heat sink so as to overcome the above problems in the prior
arts.

SUMMARY OF THE INVENTION

[0008] The primary objective of the present invention is to provide a
radiation heat dissipation LED structure, which includes a sapphire
substrate, an LED epitaxy layer, a base substrate, a radiation heat
dissipation film and a thermally conductive binding layer. The LED
epitaxy layer is formed on the sapphire substrate. The radiation heat
dissipation film is formed on the base substrate, and the thermally
conductive binding layer is provided between the sapphire substrate and
the radiation heat dissipation film so as to bind the sapphire substrate
and the base substrate in order to form the radiation heat dissipation
LED structure of the present invention.

[0009] The radiation heat dissipation film consists of a mixture of metal
and nonmetal and the surface of the film has a microscopic structure with
crystal which has a grain size of several nm to several μm. In
particular, the radiation heat dissipation film has high efficiency of
heat dissipation and can fast transfer the heat generated by the LED
epitaxy layer outwards through the base substrate by thermal radiation.
Therefore, the working temperature of the LED epitaxy layer is greatly
reduced so as to enhance the stability of light emitting and the
lifetime. Furthermore, the conducting current in the LED epitaxy layer is
allowed to considerably increase such that the efficiency of light
emitting is effectively improved. Meanwhile, the leadframe and the
aluminum heat sink are no longer needed in the present invention such
that the material and manufacturing cost is reduced. Additionally, it is
possible to reduce the weight and volume of the radiation heat
dissipation LED structure, and hence expand the application scope and
improve the convenience in usage.

[0010] Another objective of the present invention is to provide a method
of manufacturing a radiation heat dissipation LED structure, including
the steps of forming the LED epitaxy layer on the sapphire substrate,
forming the radiation heat dissipation film on the base substrate, and
binding the sapphire substrate and the base substrate by the thermally
conductive binding layer so as to form the radiation heat dissipation LED
structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention can be understood in more detail by reading
the subsequent detailed description in conjunction with the examples and
references made to the accompanying drawings, wherein:

[0012] FIG. 1 is a view showing the LED structure in the prior arts;

[0013]FIG. 2 is a schematic view showing a radiation heat dissipation LED
structure according to one embodiment of the present invention;

[0014]FIG. 3 shows a flow diagram of a method of manufacturing the
radiation heat dissipation LED structure according to the present
invention; and

[0015]FIG. 4 is a schematic view showing a radiation heat dissipation LED
structure according another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] The present invention may be embodied in various forms and the
details of the preferred embodiments of the present invention will be
described in the subsequent content with reference to the accompanying
drawings. The drawings (not to scale) show and depict only the preferred
embodiments of the invention and shall not be considered as limitations
to the scope of the present invention. Modifications of the shape of the
present invention shall too be considered to be within the spirit of the
present invention.

[0017]FIG. 2 illustrates the radiation heat dissipation LED structure
according to one embodiment of the present invention. As shown in FIG. 2,
the radiation heat dissipation LED structure 100 of the present invention
includes an LED epitaxy layer 110, a sapphire substrate 120, a thermally
conductive binding layer 130, a radiation heat dissipation film 140, a
base substrate 150, at least one electrical connection line (not shown)
and a package body (not shown). The LED epitaxy layer 110 consists of at
least an N type semiconductor layer, a semiconductor light emitting layer
and a P type semiconductor layer, which are sequentially stacked. For
instance, the N type semiconductor layer is an N type GaN (gallium
nitride) layer, the semiconductor light emitting layer may consists of
gallium nitride or indium gallium nitride, and the P type semiconductor
layer is a P type GaN layer. Further, the P type semiconductor layer and
the N type semiconductor layer are respectively connected to a positive
end and a negative end of an external power source (not shown) by the at
least one electrical connection line. The semiconductor light emitting
layer can emit light when the LED epitaxy layer 110 is forward biased (or
turned on) due to electron-hole recombination.

[0018] The package body consists of silicone or epoxy resin used to
enclose the LED epitaxy layer 110 for protection. Meanwhile, the package
body may consists of certain amount of appropriate Phosphor powder which
can convert part of the original light generated by the LED epitaxy layer
110 into excited light with different wavelength. The excited light is
then mixed with the remaining part of the original light to form
resulting light. For example, blue light as the original light can be
converted and mixed to form white light with a specific color temperature
(CT).

[0019] The thermally conductive binding layer 130 with high thermal
conductivity is provided between the sapphire substrate 120 and the
radiation heat dissipation film 140. The thermally conductive binding
layer 130 can propagate the heat generated by the LED epitaxy layer 110
through the sapphire substrate 120 towards the radiation heat dissipation
film 140. That is, the heat generated by the LED epitaxy layer 110 is
transferred to the radiation heat dissipation film 140 through the
sapphire substrate 120 and thermally conductive binding layer 130 by
thermal conduction. More specifically, the thermally conductive binding
layer 130 may consist of silver paste, tin paste, copper-tin alloy or
gold-tin alloy.

[0020] The radiation heat dissipation film 140 is formed on the base
substrate 150 such that the surface of the radiation heat dissipation
film 140 in contact with the base substrate 150 has high efficiency of
thermal radiation. Therefore, the radiation heat dissipation film 140 can
propagate the heat towards the base substrate 150 by the mechanism of
thermal radiation R, as shown in FIG. 2.

[0021] The radiation heat dissipation film 140 primarily consists of a
mixture of metal and nonmetal, which consists of at least one of silver,
copper, tin, aluminum, titanium, iron and antimony, and one of oxide,
nitride and inorganic acid of at least one of boron and carbon. For
instance, the radiation heat dissipation film 140 may consist of halide
of titanium antimony. Additionally, the radiation heat dissipation film
140 has a microscopic structure with crystal, which has a grain size
between one nanometer and tens of micrometers. It is believed that the
crystal formed in the radiation heat dissipation film 140 can induce some
specific lattice resonance to strongly emit corresponding thermal
radiation, such as infrared or far infrared.

[0022] To improve the property of the radiation heat dissipation film 140,
the base substrate 150 formed of suitable material is selected. For
example, the difference between thermal expansion coefficients of the
radiation heat dissipation film 140 and the base substrate 150 is not
greater than 0.1%.

[0023] In the above-mentioned radiation heat dissipation LED structure
100, the base substrate 150 serves as the heat sink without an additional
leadframe or heat sink so as to reduce the manufacturing cost. In
particular, the traditional heat sink such as aluminum heat sink is
considerably huge and heavy. However, if the aluminum heat sink is used,
the aluminum heat sink is possibly higher than the radiation heat
dissipation film 140 because of thermal radiation for heat dissipation.
Therefore, the radiation heat dissipation LED structure 100 of the
present invention can improve the efficiency of heat dissipation for the
LED epitaxy layer, simplify the whole LED structure and further reduce
the complexity of the design so as to increase the yield. Moreover, the
weight and volume are greatly reduced to improve the convenience and
expand the application scope.

[0024] Additionally, a small heat sink (not shown) can be connected to the
base substrate 150 to enhance heat dissipation effect, and the radiation
heat dissipation film 140 can propagate the heat to the small heat sink
by thermal radiation such that the small heat sink is possibly higher
than the LED epitaxy layer 110, which is the only heat source. It is
apparent that the mechanism of heat dissipation used in the present
invention has a considerable effect different from the traditional
scheme. According the actual measurements, the temperature of the
radiation heat dissipation film 140 can be up to 125° C. when the
temperature of the LED epitaxy layer is 115° C.

[0025]FIG. 3 illustrates the flow diagram of the method of manufacturing
a radiation heat dissipation LED structure according to the present
invention. As shown in FIG. 3, the method of the present invention
includes the steps S10 to S50. First, the method of the present invention
begins at the step S10, which is performed to form the LED epitaxy layer
on the sapphire substrate. Next, in the step S20, the radiation heat
dissipation film is formed on the base substrate. More specifically, a
slurry mixture consisting of a solvent and the mixture of metal and
nonmetal is sprayed and coated onto the base substrate which is heated
such that the solvent evaporates to leave the solid mixture of metal and
nonmetal on the base substrate and the radiation heat dissipation film
with crystal is formed.

[0026] The solvent used in the step S20 may consist of at least one of
water, alcohol and ketone, and the mixture of metal and nonmetal is
similar to what is described above with respect to FIG. 2. Thus, the
detailed description of the mixture of metal and nonmetal is omitted
herein for the sake of brevity.

[0027] Next, the thermally conductive binding layer is used to bind the
sapphire substrate and the radiation heat dissipation film to form the
radiation heat dissipation LED structure in the step S30. In the step
S40, the electrical connection lines are then used to connect the LED
epitaxy layer to the positive and negative ends of the external power
source. Finally, the LED epitaxy layer is enclosed by the package body in
the step S50. The effect of the package body is described above with
respect to FIG. 2.

[0028] The method further comprises another step of connecting an
additional heat sink to the base substrate to further enhance heat
dissipation effect, just like the above-mentioned with respect to FIG. 2.

[0029]FIG. 4 schematically illustrates another embodiment of the
radiation heat dissipation LED structure according to the present
invention. As shown in FIG. 4, the radiation heat dissipation LED
structure 102 of the present invention includes an LED epitaxy layer 110,
a sapphire substrate 120, a first radiation heat dissipation film 141, a
thermally conductive binding layer 130, a nano-enamel layer 160, a second
radiation heat dissipation film 142, a base substrate 150, at least one
electrical connection line (not shown) and a package body (not shown).
Specifically, the LED epitaxy layer 110 is formed on the upper surface of
the sapphire substrate 120, the first radiation heat dissipation film 141
is formed on the lower surface of the sapphire substrate 120, the second
radiation heat dissipation film 142 is formed on the base substrate 150,
the nano-enamel layer 160 is formed on the second radiation heat
dissipation film 142, and the thermally conductive binding layer 130 is
used to bind the first radiation heat dissipation film 141 and the
nano-enamel layer 160 to form the radiation heat dissipation LED
structure 102.

[0030] The first radiation heat dissipation film 141 and the second
radiation heat dissipation film 142 are similar to the radiation heat
dissipation film 140 as mentioned above. Besides, the LED epitaxy layer
110, the sapphire substrate 120, the thermally conductive binding layer
130, the base substrate 150, the at least one electrical connection line
and the package body in this embodiment are also similar to the
embodiment in FIG. 2. In particular, the difference between thermal
expansion coefficients of the first radiation heat dissipation film 141
and the sapphire substrate 120 is not greater than 0.1%, and another
difference between thermal expansion coefficients of the second radiation
heat dissipation film 142 and the base substrate 150 is not greater than
0.1%.

[0031] The nano-enamel layer 160 is formed by sintering the nano-particles
at high temperature to have a nano-surface. For example, the nano-surface
of the ano-enamel layer 160 has a roughness Ra of 10 to 2000.
Specifically, the nano-particle is made of aluminum oxide.

[0032] Therefore, one aspect of the present invention is that the heat
generated by the LED epitaxy layer is primarily propagated in the way of
thermal radiation by the first radiation heat dissipation film through
the thermally conductive binding layer and the nano-enamel layer towards
the second radiation heat dissipation film, and then the second radiation
heat dissipation film propagates the heat from the nano-enamel layer
towards the base substrate so as to achieve faster and more effective
heat dissipation. Therefore, the efficiency of heat dissipation for the
whole radiation heat dissipation LED structure is greatly increased.

[0033] Although the present invention has been described with reference to
the preferred embodiments, it will be understood that the invention is
not limited to the details described thereof. Various substitutions and
modifications have been suggested in the foregoing description, and
others will occur to those of ordinary skill in the art. Therefore, all
such substitutions and modifications are intended to be embraced within
the scope of the invention as defined in the appended claims.

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